This is a proposal to collect the necessary data for FDA regulatory approval of the Cytonics assay as a diagnostic tool to identify patients who will respond to steroid injection therapy for LBP due to radiculopathy. Low back pain (LBP) syndromes include spinal degenerative conditions with and without nerve root or cauda equina irritation. These syndromes represent some of the most common reasons for patients to seek medical attention. LBP syndromes associated with neurological irritation are often effectively treated, whereas those not primarily associated with neurological irritation have proven resistant. The greatest current challenge in the clinical care of patients with LBP syndromes is identifying those who suffer from active neurological irritation and therefore may benefit from interventional therapies, such as corticosteroid injection (ESI). However, there is currently no validated test to discriminate between patients who will or will not respond to ESI. For example, only ~50% of the >10 million yearly epidural steroid injections successfully relieve pain. Many patients that don't respond to initial steroid injections will receive follow-up injections at the same or a different spinal location. These unnecessary injections are costly and have side effects. In Phase I, we developed and validated an assay that can prospectively identify patients who will respond to steroid treatment. Our Specific Aim in Phase II is to collect the necessary data for FDA regulatory approval of the Cytonics assay as a diagnostic tool to identify patients who will respond to steroid injection therapy for LBP due to radiculopathy. To achieve this Objective, we will carry out the following Tasks: Task #1: Validate our assay to meet FDA manufacturing guidelines. Task #2: Carry out a large prospective study appropriate for obtaining PMA clearance using our validated assay. Task #3: Prepare and submit a PMA to the FDA. The assay will be sold as a kit, complete with all of the reagents required for the assay. We will provide the diagnostic kit to CLIA labs that are interested in providing the testing service, many of which will be located in surgical hospitals or outpatient centers. We will utilize a network of medical product distributors to provide information on the diagnostic to spine surgeons, neurologist, and pain management specialists in an effort to encourage the use of the test for their patients. We will also publish and present extensively on results of using our product. Phase II will result in a diagnostic assay to be submitted for FDA approval. PUBLIC HEALTH RELEVANCE: This is a project to develop a diagnostic assay that helps physicians know when to use steroid injections for treating back pain. Currently, 10 million such injections are made each year at a cost of about $2000 per injection. Half of the injections are ineffective. Our assay will allow physicians to know when a patient will not respond to an injection, thereby avoiding the needless injections and saving about 10 billion dollars per year in ineffective treatments, as well as allowing the physician to focus on treating the patient more effectively.